The invention relates to a medical instrument for creating an access for a minimally invasive intervention, which instrument has a body.
The body is mostly in the form of a cylindrical sleeve which is driven into the human body via an incision in the skin in order to gain access to a cavity in the interior of the human body.
In laparoscopy, the inner cavity is the abdominal cavity of the body, while in arthroscopy it is, for example, the interior of a joint.
Particularly in laparoscopy, a procedure in which minimally invasive interventions have been widely employed, this access is made via trocars. A trocar is composed of a trocar sleeve, which has a tube measuring approximately 10 cm in length with a housing arranged at the proximal end thereof. The housing in most cases accommodates valves, in order to seal the housing off in relation to lateral connection pieces via which it is possible to introduce, for example, gases for inflating the abdominal cavity or liquids for irrigation. At the proximal end, the trocar housing is provided with a seal that in most cases has a central opening through which, after the trocar sleeve has been fitted, instruments can be pushed into the body, for example endoscopes for visual monitoring, or other surgical instruments.
To put the trocar in place, a trocar mandrel is pushed into the trocar sleeve from the proximal direction, which trocar mandrel is designed such that its sharp tip, in most cases in the shape of a triangle, protrudes past the distal end of the trocar sleeve. A small incision measuring approximately 1 cm in length is made in the skin, the trocar, or the tip of the trocar mandrel protruding from the distal end of the trocar sleeve, is placed on the incision, and the assembly is then pressed through the abdominal wall. Thereafter, the trocar mandrel is withdrawn, and the trocar sleeve is then free to allow a minimally invasive intervention to be performed through it.
In laparoscopy, the trocar sleeve has to be pushed through the abdominal wall which, in humans of normal build, is a few centimeters thick. Several hoses are often connected to the proximal end of the trocar sleeve, and some instruments, for example surgical forceps, protrude very far past the proximal end of the trocar sleeve.
As a result, considerable tilting moments act on the trocar sleeve fitted in the body, thus posing the risk of the trocar tilting laterally from its original orientation.
Since the connected equipment also exerts a force in the direction of gravity in the case of vertical trocars, it may happen that the trocar sleeve moves axially in an undesired manner. A movement in the distal direction can be compensated by the operator to some extent by pulling on the trocar. However, if the trocar is pulled too far in the proximal direction, for example because an instrument to be withdrawn through the trocar sleeve has caught on the distal end of the trocar sleeve, there is a danger of the entire trocar slipping out of the body.
This tilting moment has an even more pronounced effect when operations are being performed in which the trocar is introduced not vertically, but in an oblique or even a horizontal direction.
Attempts were therefore made to hold access instruments of this kind more securely or more effectively on the body.
U.S. Pat. No. 3,717,151 discloses an access cannula in the form of a trocar having, at the distal end, expandable fingers that are oriented in an axial direction for insertion into the body and, after the abdominal wall has been penetrated, can be spread out laterally by an expansion mechanism. Before the sleeve is withdrawn, the expanded fingers then have to be retracted again to allow the cannula to be withdrawn again from the body.
This structure requires a complicated mechanism for controlling the expandable fingers.
US 2008/0234550 A1 describes a minimally invasive access port in which the sleeve, which is pushed into the body, has laterally pivotable plates which, for insertion purposes, can be pivoted in to form a slender body and can then be spread open by an expansion mechanism when in the body.
A disadvantage of these devices is that a complicated mechanism has to be present for expanding and retracting the expandable elements, and this requires a complex structure.
This structure includes numerous corners or niches in which bacteria are able to adhere, such that these devices can be cleaned only with great difficulty, or they have to be dismantled prior to each cleaning procedure.
It should be noted that, in an operation performed in the abdominal cavity for example, four, five or six trocars are inserted in order to allow the various manipulations to be carried out, and, after an intervention has been performed, the trocars have to be made available as quickly as possible for a further intervention.
The object of the present invention is therefore to create an access instrument that has a simple structure and is easy to handle and that can be anchored reliably.